\section{User interface}
The first user interface will only be command line.

The user will give a xml file as argument of the command call. Eventually a configuration for the ray tracing engine could be given. If no configuration file is given, the software will check if a file called .raytracer.xml exists in the home directory of the user (ie. $\widetilde{}/.raytracer.xml$). If not, the default parameters will be used.

Standard call :

  \texttt{\$\ raytracer -s scene.xml}

Diffenrent outputs will be provided by the program. The image must be printed on screen and also writted in a file.

